Insulin

Insulin is produced in the pancreas and is the key that lets sugar (glucose) out of the blood and into muscle, liver and fat cells. It rises after every meal containing carbohydrates or protein, distributes the energy and then falls again. Without insulin, the sugar would stay in the blood – which is what happens in type 1 diabetes. It was discovered in 1921 by Frederick Banting and Charles Best and has saved millions of lives since.

Insulin is a building and storage hormone: as long as levels are high, the body fills up its stores and puts the brakes on fat breakdown. This gave rise to the myth that insulin alone makes you fat and that all you need to do is avoid carbohydrates. Research shows, however, that what decides whether you gain or lose fat is your energy balance over the whole day. In controlled studies, people eating the same number of calories lost a similar amount of weight, whether their diet was low-carb or low-fat. Rises in insulin after eating are normal and healthy.

Insulin resistance, on the other hand, is a real problem: when cells respond less well to insulin – mainly because of a lot of belly fat, too little exercise, too little sleep and genetic predisposition – the pancreas has to release more and more of it. Blood sugar still stays high, hunger increases, and over the years type 2 diabetes can develop. Everyday warning signs: a large waist, tiredness after carb-heavy meals and a constant appetite.

The good news: hardly anything improves the action of insulin as quickly as exercise. Working muscles take up sugar even without insulin, and losing just 5 to 10% of your weight markedly reduces resistance. Fibre, wholegrains, protein at every meal and enough sleep help too. If insulin resistance is suspected, your GP can measure your fasting blood sugar and long-term blood sugar (HbA1c) and talk you through what the results mean.